Our own astronomers have, long ago, computed the distance of Hesperos from the sun, her magnitude, density, time of rotation on her axis, and a few other particulars. Some of these computations are approximately right, but they have considerably over-estimated her distance from the sun, which is really not much over sixty-six millions of miles. And with respect to the physical geography, or more properly, Hesperography of the planet, they are, all of them, in absolute ignorance, and that for the best of possible reasons—no human being but myself has ever seen her surface. Improvements in the telescope will never enable the terrestrial astronomers to penetrate the permanent stratum of cloud which, at an average elevation of twenty miles, surrounds the entire planet like a screen. The visible disk of Hesperos is simply the outer surface of this cloud-screen, which reflects the solar rays very copiously. The Hesperian atmosphere is of immense density, for the average height at which mercury stands in a tube constructed after the method of Signor Torricelli is somewhat over fifty-nine inches. It is fortunate that, except in the equatorial region, storms are unknown, for the impact of a hurricane of air of such density would be fatal to most forms of life. This ponderous atmosphere supports the stratum of cloud just mentioned, which is sufficiently dense to act as a screen against the solar rays, and it thus renders the climate of the greater part of the planet by no means unpleasant. Though the supply of solar heat is nearly double of that received by the earth, I never, during my two years’ residence in Hesperos, experienced as much inconvenience from that source as I have frequently met with in our own tropical countries. The planet is divided into two regions, which in ancient times were supposed to be, and, in one respect, really were, mutually inaccessible. The division is made by an immense equatorial ocean which surrounds the entire globe. The extent of this ocean, measured from north to south, is nowhere less than four thousand miles. Each of the poles is the centre of a vast continent which extends on all sides till it meets the great central ocean. The margins of these continents are exceedingly irregular in shape, being broken by arms of the sea, which often run up the country for many hundreds of miles. Many islands, some of which are of considerable size, are scattered through the ocean, but none of these lie at a very great distance from the mainland. The entire surface is nearly equally divided between land and water, this distribution forming a marked contrast with the present state of the earth.